Naloxone has a printed expiration date of 2 to 3 years.
However, naloxone has been proven to be extremely effective more than 30 years after its expiration.
If for some reason you do not want expired naloxone, NEVER throw it away. Donate it to your local syringe service program, recovery program, or NEXT Distro.
Ideally, naloxone should be kept at room temperature and aware from sunlight, but naloxone is still effective even if frozen or overheated. Frozen naloxone must be thawed before it can be used. Additionally, naloxone vials that have been overexposed to sunlight can sometimes become yellow or chunky–as long as the liquid in the vial is still clear, then you are in the clear to use it.
Effect of Extreme Temperature on Naloxone Nasal Spray Dispensing Device Performance, Cambridge University Press
The effects of heat and freeze-thaw cycling on naloxone stability, Harm Reduction Journal